As Nigeria celebrates two years of being polio-free health, authorities in the country are keeping a watchful eye for any new cases.

Nigeria, which reported more than half the world’s polio cases in 2012, recently said that it was awaiting certification of being polio-free from the World Health Organization (WHO) in 2017. The polio-free certification is granted by the WHO when no case of polio is reported from a country for two consecutive years. Nigeria was removed from the list of polio-endemic countries in 2015.

Nigerian President Muhammadu Buhari tweeting on his official Twitter account noted, “We’re committed to making the certification a reality, by supporting routine immunization, and revitalizing our primary health care system.”

Poliomyelitis or polio, an infectious disease that mainly affects children and which sometimes lead to paralysis of limbs is caused by the poliovirus. In about one percent of cases affected by poliomyelitis there is muscle weakening that result in an inability to move. Most but not all people afflicted with polio recover; nearly four percent of children and 23 percent of adults affected by muscle weakening, eventually die.

In 2015, the number of people affected by polio was less than 100 — appreciably down from the 350,000 cases reported in 1988. Polio eradication could be another success story for global health, provided the two remaining pockets of the disease, Afghanistan and Pakistan, are able to eradicate the virus. Nigeria, which was a third remaining country afflicted with polio, has not reported any new cases since 2015